ul,ol{
    list-style: none;
    margin:0;
    padding:0;

}
/* .clearfix::after{
    content: '';
    display: block;
    clear: both;
} */
/*--- 一级菜单 -------*/
.menu-item{
    float: left;
    /* width: 100px; */
    background-color: lightblue;
    height: 50px;
    text-align: center;
    border:1px solid red;
    position: relative;
}
.menu-item a{
    line-height: 50px;
    color: #eee;
    text-decoration: none;
    background-color:black;
    padding:13px 20px; 
}
.menu-item:hover .sub-menu{
    display: block;
}

/*----- 二级菜单 -------*/
.sub-menu{
    display: none;
    position: absolute;
    left:0;
    top:51px;
    width: 100%
}
.sub-menu .sub-menu-item{
    background: blue
}
.box{
    width: 100px;
    height: 100px;
    display: inline-block;
    background-color:red;
}
.big{
    height: 50px;
    background-color: green;
}